Is it dangerous to use the microwave without a duct cover

Your magnetron is overheating, which can be caused by:

• operating oven without cover(s) in place
• wrong magnetron installed in oven
• an old or otherwise failing magnetron
• cracked magnetron magnet
• improper power line voltage (should be 110-125VAC)
• foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
• failed or inoperable cooling fan or hood vent exhaust fan
• deteriorating foam weatherstripping seals in air ducts or on outside cover
• blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
• clogged or greasy charcoal filter or grease filter
• blocked duct in hood vent exhaust

The first suspects in my book are fan failure, blocked vents, or bad magnetron.

You at least have a faulty "start" switch and probably a faulty door safety interlock switch and maybe a faulty latch. You can remove the cover and start checking the switches with your VOM if you like. Unless you are handy and can do this work yourself, it is probably not economical to have this repaired by a professional. Do not touch the capacitor. this (usually silver) can device is electrically very dangerous.

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If you unplug the oven and let it sit a while to make sure that the capacitor has discharged, and you're careful, there's no problem with changing the lamp yourself. You need to remove the cover to get at it, and it's a special lamp with a mounting tab that secures it to the plastic duct covering the magnetron tube. I don't recall if this oven uses tamper-resistant screws, the Torx type with center pin that requires a special driver. If it does use these screws, you can find driver bits with little trouble today.

The Sharp part number is RLMPTA087WRZZ. Here's one source I use frequently, and there are many more appliance parts sellers online. You might also find a suitable replacement lamp if there's a well-stocked appliance parts store in your area.

Faulty Magnetron or Power supply for it.

DO NOT try to REPAIR this Inverter Power Supply (U) and also DO NOT RE-ADJUST PRESET VOLUME on the board. It is very dangerous to repair or adjust without sufficient test equipment because this circuit handles very high voltage and very large current. Off alignment or inverter board operation is dangerous. Operating a misaligned inverter circuit is dangerous due to the very high voltage and current that is produced by this board. Defective boards must be replaced with a new one.
Consult an approved Panasonic Microwave Repair Service.

H97, H98 and H99 appears in display window a short time alter start key is pressed and no microwave oscillation.

NOTE:

DO NOT try to REPAIR this Inverter Power Supply (U) and also DO NOT RE-ADJUST PRESET VOLUME on the board. It is very dangerous to repair or adjust without sufficient test equipment because this circuit handles very high voltage and very large current. Off alignment or inverter board operation is dangerous. Operating a misaligned inverter circuit is dangerous due to the very high voltage and current that is produced by this board. Defective boards must be replaced with a new one.

i wont worry about it. it is for grease ewntrapment

If you can get to the top screws without pulling the unit down then you can do the job. Sometimes though it goes back together and alignment is simpler if it is on a table and the cabinet is off. I have successfully done it both ways but neither is what I consider easy.
eric

You have a short to ground. It's a very dangerous situation. Stop work, call an electrician!

If a plastic scrubber won't clean it, then when it's dry, you may be able to place duct tape or packing tape over it, press and rub it firmly, and remove the tape. It may remove much of the debris.

A can of compressed air (in the computer section of Wal-Mart, for example) may blast out the bits.

If it resists all efforts, it may be necessary to take to the outer cover off, peel off the plastic light cover sheet, do the cleaning, then install a new light cover sheet.

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first remove mains cord from main power. and remove the microwave oven top cover and check the bulb and crefully remove the old bulb and put new bulb. at high voltagae section dont touch any thing ,that area very dangerous ,thats why very carefully work inside the microwave oven ..